Problem: Simplify the following expression: $\sqrt{90} - \sqrt{10}$
Solution: First, try to factor any perfect squares out of the radicals. $= \sqrt{90} - \sqrt{10}$ $= \sqrt{9 \cdot 10} - \sqrt{10}$ Separate the radicals and simplify. $= \sqrt{9} \cdot \sqrt{10} - \sqrt{10}$ $= 3\sqrt{10} - \sqrt{10}$ Finally, simplify by combining the terms. $= ( 3 - 1 )\sqrt{10} = 2\sqrt{10}$